Currently, many engine blocks and engine parts are made of aluminum to provide a lighter weight vehicle. When using aluminum, it is necessary to treat the surface with chromic acid to remove oxides so as to improve paint adherence. In so doing, a very faint light gold appearance is obtained on the aluminum part. However, in today's modern factories, wherein sodium vapor lights are used, it is sometimes very difficult for a person to visually detect the presence of a chromate coating. Up until now, the presence of such a coating could only be positively identified by a very time consuming analysis of atomic absorption. Therefore, there is a desire in the industry to provide a fast, on-the-spot and reliable means of detecting the presence of a chromate coating on aluminum parts which are to be painted.
Now a method and composition have been invented for detecting such a coating.